During the current year we have: 1) analysed glutamine synthetase specific activity levels in cultured mouse teratoma cells (Exp. Cell Res. 94: 459 (1975)), 2) developed a quantitative method for measuring topography of cell surface carbohydrate-containing receptor sites on specific cell populations and parts of a single cell (Concanavalin A as a tool, Wiley, 293 (1976), 3) used this assay to determine the mobility of lectin receptor sites on specific cell populations (Nature 258: 342 (1975), 4) determined that teratoma cell adhesion factor (TAF) consists of 2 components purified on DEAE cellulose and analysed these components on gel electrophoresis, 5) determined that an active cell binding site on TAF is D-galactose (Exp. Cell Res. 92:122 (1975) and 6) showed that the optimum cell surface configuration for tumor cell interactions to occur (lectin-mediated) is one of broad projections not numerous narrow microvilli (J. Cell Biol., in press (1976). In coming years we hope to: 1) examine in detail the nature and role of carbohydrate-containing cell surface receptor sites in tumor and normal cell adhesion, 2) continue analysis of the 2 components of TAF and TAF cell surface receptor sites, 3) examine the relationship between glutamine synthetase specific activity and tumor cell adhesiveness in vitro, 4) determination of a role for glycosyl transferase-acceptor interactions in tumor and normal cell adhesion and in ascites tumor cell adhesion factor-mediated cell aggregation. BIBIOGRAPHIC REFERENCES: (1976) Oppenheimer, S.B., Biology and Cultivation of Teratoma Cells, in Tests of Teratogenicity in Vitro, North Holland, Amsterdam, 261-274. (1977) Oppenheimer, S.B., Interactions of Lectins with Embryonic Cell Surfaces, in Current Topics in Developmental Biology, Edit. Moscona & Monroy, Academic Press, in press.